With both parties looking for momentum heading into November, a member of a distinguished Democratic family faced a Republican former lawmaker in a special election Tuesday to fill the House seat of Bill Janklow (search), who went to jail over a deadly auto accident.

Lawyer Stephanie Herseth (search), 33, held a solid lead in the most recent polls in this GOP-leaning state against Republican Larry Diedrich, 46, a farmer who served in the Legislature and was head of the American Soybean Association.

The winner of Tuesday's race takes office immediately and will serve out the seven months left in Janklow's term. Both candidates will meet again in November to compete for a full two-year term. One, however, will have the advantage of incumbency.

The Democrats were looking not only to gain a House seat but to get a good running start on the November elections. The Democrats took a House seat away from the GOP earlier this year in a special election in Kentucky. (Still, the Democrats must pick up a dozen more seats in the general election to gain control of the House.)

Underscoring just how closely watched the race is, the Republican and Democratic House campaign committees waged media blitzes in South Dakota, pouring $2 million into TV ads in a rural state of just 765,000 people. In March, Vice President Dick Cheney (search) campaigned for Diedrich in South Dakota.

Diedrich and Herseth have both supported President Bush on the war in Iraq. The campaign has instead focused on prescription drugs, Medicare, Bush's tax cuts and veterans issues.

Diedrich has said he supports making the Bush tax cuts permanent, and his television ads say Herseth is against it. Herseth has said the ads are misleading and she wants to make many, but not all, of the cuts permanent.

Diedrich opposes abortion, while Herseth favors abortion rights. Both candidates support a constitutional amendment to ban gay marriage.

Janklow, a former South Dakota governor, resigned from Congress in January after being convicted of manslaughter in an auto accident that killed a motorcyclist. He served 100 days in jail and was released last month.

Herseth's grandfather was governor and her father a longtime state lawmaker, and she gained name recognition from running a close race against Janklow in 2002.

She pledged a clean campaign against Diedrich, viewed as a smart move in light of South Dakotans' response to a nasty battle between two gubernatorial candidates in 2002 that ended when a third, lesser-known candidate won.

Herseth has raised more than $1.8 million, Diedrich nearly $1.3 million.

Diedrich was counting on a large Republican turnout. The latest voter registration figures showed 224,506 Republicans, 180,282 Democrats and 59,081 independents.

Elsewhere Tuesday, Alabama voters chose Republican nominees for three seats on the Alabama Supreme Court — races that became a referendum on ousted Chief Justice Roy Moore and his Ten Commandments monument. Moore was expelled from the bench by a judicial ethics panel for refusing to remove the 21/2-ton granite monument from the state courthouse rotunda.

"That's the question I get again and again on the campaign trail: How would you have voted on the removal of the Ten Commandments monument?" says Tom Parker, a former Moore aide running for the high court.

The Ten Commandments dispute also figured in the GOP primary for a U.S. House seat. Moore's attorney, Phillip Jauregui, challenged six-term Rep. Spencer Bachus for the Republican nomination.